Receiver and barrel coupling

ABSTRACT

For an automatic or semi-automatic weapon or gun an arrangement for aligning and coupling together the weapon receiver and barrel groups that includes a pin secured within and across the receiver interior to receive and seat a lateral slot formed in the barrel, the pin for aligning and functioning as a pivot point for seating the barrel into the receiver, the receiver further including a screw journaled through the receiver bottom portion, a threaded end thereof to align with and turn into a threaded hole formed in the barrel undersurface when said barrel lateral slot is seated on the pin, the screw including a head without the receiver for manual turning.

This is a division of application Ser. No. 580,366, filed Feb. 15, 1984,now U.S. Pat. No. 4,573,394.

BACKGROUND OF THE INVENTION

1. Field

This invention relates generally to automatic firing guns, specificallyto a type of gun known as a submachine gun and, more particularly, to asimplistic assembly arrangement for rigidly coupling together the gunsubassemblies.

2. Prior Art

The value of any gas-operated projectile firing weapon, whether it be ofa large or small caliber, is its accuracy and reliability for deliveringfire on target. The market for automatic weapons is with law enforcementagencies and the military, where the weapon must sometimes be operatedunder adverse conditions and, yet, will still function reliably todeliver accurate fire on target. It is essential with fully automaticweapons, such as a machine gun or submachine gun, that the weapon fireconsistently without jamming.

The present invention is an evolutionary outgrowth of and improvement oncertain other U.S. patents; specifically, patents by R. J. Casull, U.S.Pat. Nos. 3,319,523 (1967) and No. 3,366,010 (1968), and later patentsby Brandstatter et al., No. 3,969,980 (1976) and No. 3,969,981 (1976).These earlier patents were a basis for development and manufacture of aweapon known as the American 180 and show and describe an efficient andreliable weapons system capable of delivering a high volume of lowcaliber fire accurately on target, with almost no barret climb, thepresent invention being an improvement thereon.

The present invention improves on the structure of the above-cited art,providing interlinking structures whereby, with only a single barrelretaining screw, the component assemblies are maintained together,holding a bullet cartridge feed block in position relative to the barreland receiver groups and in alignment with a cartridge feed opening of adrum-type magazine. So arranged, cartridges fed from the magazine willbe exactly aligned by the feed block for pickup from the undersurfacethereof, in turn, by a reciprocating bolt. The bolt movement, inconjunction with the cartridge feed block mechanism, cams the cartridgeoff the feed block undersurface into the barrel breech for firing, withback travel of the bolt pulling spent cartridge casings from the barrelbreech and ejecting them from a receiver cartridge exhaust. Where earlyarrangements, including the above-cited patents, have involved a numberof pins, screws, bolts, or the like for fitting through aligned openingsof the respective weapon groups, the present invention, by itsinterlocking assemblies, provides a gun that can be assembled anddisassembled in a phenomenally short period of time, where the componentassemblies are tightly coupled and the relative distance between thereceiver and barrel groups is fixed to provide an optimum head spacingbetween the firing pin and the barrel breech. In a field setting, aperson, with only a basic familiarity with the weapon, and littleinstruction, can easily assemble and disassemble the gun and performbasic cleaning and oiling thereof, including replacement of componentssuch as the bolt.

SUMMARY OF THE INVENTION

It is, therefore, a general object of the present invention to providean improved submachine gun of a type that utilizes a drum-type magazineand that utilizes interlocking components such that the weapon is heldtogether by a single screw coupling.

Another object of the invention is to provide an improved connector lessreceiver top strap retaining arrangement whereby a top strap forcovering over an open top portion of the weapon receiver, maintainingthe reciprocating bolt therein is manually fitted over or removed fromcovering engagement to the receiver.

Another object of the present invention is to provide an interlockingarrangement between the receiver and barrel groups for exactlypositioning and maintaining a cartridge feed block in alignment to adrum-type magazine cartridge discharge and aligned with the barrelbreech, and for fixing and maintaining the head space distance betweenthe barrel breech and a firing pin end of the reciprocating bolt.

Still another object of the present invention is to provide a simplisticarrangement of components of a submachine gun, whereby the componentsare arranged to securely interlock such that the weapon can be easilybroken down and reassembled.

In accordance with the above objects, the present invention includesimprovements to certain component assemblies or groups of a submachinegun commonly known as the American 180. The components and theirinterconnection arrangement interlock such that, with a single screwcoupling only, a barrel group is locked into a receiver group, bothfixing the head space distance of the barrel breech to the firing pinand maintaining a cartridge feed block therewith to align a throatthereof in exact alignment to a cartridge exhaust of a drum-typemagazine and with the barrel breech. Top strap locking to a receiver topportion is provided by including with the top strap spaced apart flangesextended outwardly from the longitudinal sides of the top strapundersurface that align with inwardly projecting rail sections formed inthe receiver longitudinal top edges, the strap flanges to slide beneaththe receiver rails as the top strap is slid rearward relative to theweapon stock. At the top strap limit of rearward travel, a spring biasedpin-lock or detent arrangement is provided to maintain that top strapcovering that portion of the receiver above the reciprocating bolt. Suchdetent includes a spring biased ball or plunger that travels into anopening in the strap end. The pin-lock or detent is easily released byapplication of a horizontal force to the top strap sight end thatovercomes the spring biasing, with the pin or plunger traveling out ofthe opening allowing the strap flanges to travel forwardly along theundersurface of the receiver rails until again aligned with the openingstherebetween whereat the top strap is free to be lifted off from thereceiver. This connector less coupling simplifies opening the weaponreceiver to provide access to the spring biased bolt therein.

The assembled receiver and strap arrangement and the single screwcoupling of the barrel group to the receiver group, in addition to theirinterlocking coupling provide for aligning and positioning a cartridgefeed block that is held therebetween a throat thereof in alignment to acartridge discharge or exhaust of a drum-type magazine. The cartridgefeed block provides a platform wherethrough the cartridge pass and arepicked up from the undersurface, in turn, by the reciprocating bolt asit moves forward in the receiver and inserts the cartridge into thebarrel breech, a firing pin thereof firing the cartridge, and an ejectoralongside the firing pin withdrawing and ejecting the cartridge casing.The cartridge feed block includes a pair of spaced apart, arcuate shapedears that extend parallel and outwardly from one end thereof forfitting, in close tolerance, into arcuate grooves formed in oppositesides of the barrel breech end, the arcuate shape thereof providing forexact alignment of the feed block relative to the barrel breech when theears are fully installed in the grooves, the other feed block end heldin place against the receiver stepped portion by an overhanging end ofthe receiver top strap installed to the receiver.

The single screw connection arrangement discussed above includes, incombination, a barrel receiving pin fitted laterally through thereceiver projecting above the receiver bottom for receivingcomplementary groove formed across the barrel, the groove positioned oftop of the pin functioning as a pivot wherearound the barrel group ispivoted into the receiver for aligning it within the receiver.Thereafter a barrel retention screw, as the single screw freewheeling inthe receiver bottom, is turned into a threaded hole in the barrel,locking the barrel group thereto. The barrel retention screw preferablyincludes a large head for manually turning the threaded end thereof intothe barrel threaded hole, the screw and the pivot exactly positioningthe barrel with regard to the receiver group, fixing the head spacedistance between the barrel breech and the bolt firing pin end.

The weapon of the present invention is unique in that it provides aninterrelationship of components whereby the weapon can easily be brokendown into individual groups and parts and reassembled, the criticalcomponents in exact alignment by manual turning of a single screw only,facilitating in-field maintenance and repair.

BRIEF DESCRIPTION OF THE DRAWING

In the drawings is shown that which is presently regarded as the bestmode for carrying out the invention:

FIG. 1 is a side elevation view of the submachine gun of the presentinvention;

FIG. 2 is a perspective view of the breech portion of the weapon barreland receiver group with components thereof exploded away from theassemblage;

FIG. 3 is a partial sectional view taken along the line 3--3 of thereceiver group of FIG. 1, showing a lateral cross-section of thereciprocating bolt, with a rear sight being omitted for clarity;

FIG. 4 is a side elevation sectional view taken along the line 4--4 ofFIG. 3, showing a section of the receiver as in FIG. 1, with thereciprocating bolt and sight rail being omitted for clarity;

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 4, showinga receiver top strap in its covering attitude over the receiver;

FIG. 6 is a view like that of FIG. 4, showing, arrow A, the top strapslid forward with flange sections thereof shown sliding out from underreceiver rail sections with, in broken lines, the top strap shown liftedoff from the receiver, arrow B;

FIG. 7 is a sectional view taken along the line 7--7 of FIG. 6, showingthe top strap flange sections free of the receiver rail sections;

FIG. 8 is an end sectional view taken along the line 8--8 of FIG. 1showing a strap locking arrangement, with the sight and sight rail forclarity, as including a plunger lock;

FIG. 9 is a view like that of FIG. 8, only showing another embodiment ofa strap lock arrangement, as including a ball check lock;

FIG. 10 is a top plan sectional view taken along the line 10--10 of FIG.1 with a drum magazine and an end of the receiver top strap removed forclarity, showing a top portion of a barrel portion broken away to exposethe breech thereof, and showing a cartridge feed block, with componentsthereof shown in broken line, the feed block installed to the receiverand aligned relative to the barrel breech;

FIG. 11 is a side elevation sectional view taken along the line 11--11of FIG. 10, showing a portion of the receiver removed to expose thebarrel fitted therein, the drum-type magazine and receiver top strap endshown in broken lines, with the cartridge feed block shown rotated inbroken lines, arrow C, and maintained in a locked attitude by anoverhanging end of the top strap end, shown in solid lines;

FIG. 12 is a profile perspective view of the preferred cartridge feedblock of the invention;

FIG. 13 is a sectional view taken along line 13--13 of FIG. 1, with thedrum-type magazine removed for clarity, showing the barrel connected bya single barrel retaining screw to the receiver group;

FIG. 14 is a view like that of FIG. 13, except the barrel retainingscrew is shown turned out of the barrel; and

FIG. 15 is a side elevation sectional view taken along line 15--15 ofFIG. 14, showing also the barrel positioning pin installed in a lateralgroove formed in the barrel.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings:

FIG. 1 shows a side elevation view of submachine gun 20 of theinvention, hereinafter referred to as "gun". Gun 20 is shown herein as agun that is capable of full automatic operation, utilizing an "openbolt" configuration. It should, however, be recognized that thedescribed gun 20 can operate in semi-automatic mode and that, withmodification to the bolt only, can be limited to semi-automaticoperation only, which arrangments are within the present disclosure andcited prior art. Gun 20 includes a stock 21 (a butt portion of which isshown broken away) a barrel group 22 that includes a hand grip 23 and afront sight 24; a trigger group 25 that includes a pistol grip 26 forholding by an operator to squeeze with his finger a trigger 27 that islocated within a trigger guard 28; and a receiver group 29 that includesa receiver 30 that includes an open rearward stepped top portion asrelating the receiver connection to stock 21, and a top strap 31 forclosing over the receiver open top. The top strap includes, on theforward end thereof, as relating to the receiver connection to thebarrel group, a drum-type magazine latch 32 with a rear sight 33 securedacross the rear end thereof. Shown in FIG. 1, the receiver 30 has alongitudinal slot 34 formed therein, wherefrom projects a knob 35a of aslide 34a for engaging and pulling rearward a reciprocating bolt 35. Asectional view of FIG. 3, shows reciprocating bolt 35 biased by coilspring 35b as it is maintained within the receiver 30. As will bediscussed later herein, the reciprocating bolt is arranged to move backand forth within the receiver, picking up cartridges from anundersurface of a throat of feed block 37, camming them into a barrelbreech end, where a fixed firing pin end, not shown, of thatreciprocating bolt strikes the cartridge primer, with an extractor ofthe reciprocating bolt face with the firing pin, not shown, thenwithdrawing the spent cartridge casing for ejection. The cartridges areserially fed into the cartridge feed block from a drum-type magazine 36,preferably like the drum shown by Brandstatter et al., U.S. Pat. No.3,969,980, that will feed, under a spring pressure, a flow of cartridgesthrough an exhaust, discharge or exit port into a throat 60 of feedblock 37, the operation of which feed block will be described in detaillater herein.

The gun 20 consists essentially of the assemblies or groups set outabove for firing a small caliber shell, preferably a twenty-two caliberconventional or magnum round, that, for an open bolt weapon firing fullautomatic, will fire at an approximate rate of eighteen hundred roundsper minute. The preferred drum-type magazine holds one hundredseventy-seven rounds and can be emptied at this rate of fire inapproximately six seconds, providing thereby a capability for placing ahigh-volume of fire on target in a very short period of time.

Several embodiments of the gun have been produced and marketed under thepatents cited earlier herein (Casull, U.S. Pat. Nos. 3,319,523 and3,366,010, and Brandstatter, et al, U.S. Pat. Nos. 3,969,980 and3,696,981) that show the prior art that this invention improves upon.The present invention, therefore, should be understood to constitute animprovement over such earlier gun in individual component assemblies andtheir interaction. Essentially, therefore, the preferred arrangements ofthe trigger group 25; the bolt 35, that functions as either an open orclosed bolt; the stock 21; and the drum-type magazine 36 are like thosecomponents incorporated in earlier weapons and are shown and describedin detail in these earlier patents, or like earlier references, andwill, therefore, not be discussed in detail herein. The disclosure ofthese earlier patents is therefore adopted by this reference.

The present invention is directed to an improved receiver 30 of thereceiver group 29, with top strap 31 arrangement; an improved feed block37 locking; and an improved barrel group 22 attachment arrangement forsecuring that barrel group to the receiver group. These assemblies andcomponents and their interrelationship with the earlier known componentsas set out in detail below provide a gun 20 that can be constructed forsemi-automatic fire only or for automatic or semiautomatic mode andprovides for rapid and efficient disassembly into component assembliesand parts by turning of a single barrel retention screw only. Suchconnection arrangement, in cooperation with the interlocked componentassemblies, serves also to fix in place the cartridge feed block in thereceiver group to exactly align throat 60 thereof in exact alignmentwith the magazine cartridge exhaust and with the barrel breech. The feedblock receives and positions each cartridge through the throat, in turn,for pick-up by the moving bolt from the undersurface thereof. With gun20 constructed to be capable of full automatic fire, the bolt is cockedby pulling bolt handle 35a rearwardly against spring biasing 35b to anopen attitude. When the trigger is pulled, the bolt moves forward, thebolt face picking up a cartridge out from the feed block throat andguiding it into a barrel breech. At the limit of forward bolt travelwith respect to the barrel breech, a firing pin projecting from thatbolt end strikes the cartridge primer, igniting the power therewithin.The back thrust of the exploding powder forces the cartridge casingagainst the bolt, pushing it back against the bolt spring biasing, theempty cartridge casing maintained by an ejector arranged on the boltface traveling therewith until the cartridge casing is ejecteddownwardly through a receiver bottom or discharge opening 58. Rearwardbolt travel then continues to a point where, if the trigger is released,a sear thereof, not shown, will engage the bolt to retain it in an openor cocked attitude. If, however, an operator continues to depress thetrigger, the sear will not engage the bolt that will continue to travelback and forth in the receiver, picking up and firing cartridges at arapid rate.

Turning to the individual component assemblies of gun 20, shown in FIG.2, the receiver group 29 includes the receiver 30, a box-like structurethat is stepped at a rearward-most top portion and is open along the topand on one end whereto the barrel group is fitted. The receiver alongthe stepped portion accomodates the bolt 35 reciprocating therein. Thetrigger group 25 is mounted in the receiver bottom with the searthereof, not shown, extending into the receiver to interrupt bolt travelby engaging a lateral groove in the bolt understructure, not shown, whenthe trigger is released. The bolt of this embodiment is thereby held inan open or cocked attitude. The receiver top is covered by installationof the top strap 31, as illustrated by broken arrow D in FIG. 2, thatshows pairs of spaced apart top strap flange sections 39 fitted throughopenings between receiver rail sections 40, and the top strap movedrearwardly, the flange sections to travel under the receiver rails 40,as shown also in FIGS. 6 and 7. The top strap is urged rearwardly by anoperator pushing with his hand on top strap forward end 41, FIG. 6, orpulling against the signt group 33, FIG. 1, to slide the flange sections39 sliding beneath the rail sections 40 to the receiver coveringattitude shown in FIG. 4. Shown in FIGS. 2 and 4, the top strap forwardend 41 includes curved grooves 42 that are inset in opposite sidesthereof, which grooves conform to the curve of receiver group ends 43.So arranged, when the top strap is moved to covering attitude over thestepped portion of the receiver open top, as shown in FIGS. 2 and 4, thecurved surfaces of the respective top strap grooves 42 will closely fitagainst the receiver ends 43, providing a barrier to further top straprearward travel. The sectional views of FIGS. 3 and 5 show the top strapflange sections 39 locked under the receiver rail sections 40, with FIG.3 showing also the bolt 35 and the a coil spring 35b for spring biasingthe bolt.

To maintain the top strap 31 in covering attitude over the top of thereceiver body 30, a hole or depression 43 is centrally formed in therearmost top strap end, flange 39, shown in FIG. 2, to align with astrap lock 44 when the strap is moved fully rearwardly as describedabove. The strap lock is a spring biased ball or detent arranged toreleasably maintain the top strap positioned over the receiver until anappropriate force is applied thereto by an operator applying ahorizontal force thereagainst with his hand to slide the top strapforward. FIGS. 8 and 9 show two different embodiments of preferreddetent-type strap lock configurations. The embodiment of FIG. 8 consistsof forming a vertical receiver hole 45 in the receiver 30 rear end 30aand positioning within that hole, as a detent, a plunger 46. The plungeris shown as a top hat design to have a rounded top and includes a widebase to rest on a spring 47 positioned therein. The plunger is retainedby a retaining O-ring 48, sleeve, or the like. So arranged, by slidingthe top strap flanges beneath the receiver rails, as illustrated byarrow D in FIG. 2, a top strap ramp 49, formed in the top strapundersurface, will engage the plunger rounded top. Further rearward topstrap travel depresses that plunger against the biasing of the spring47, until the plunger end aligns with the receiver hole 45, whereat theplunger rounded end will travel into that hole, providing thereby alocking of the strap to the receiver. This locking can be overcome, asby a person pushing horizontally with the heel of his hand against thetop strap rear sight 33 to urge that plunger end from the hole 45, withtop strap travel compressing spring 47, until ramp 49 is reached.Further top strap travel toward the barrel group slides the flangesections 39 out from under the receiver rail sections 40 to the attitudeshown in FIG. 6, where the top strap can be lifted off from thereceiver.

FIG. 9 shows another embodiment of a strap lock 50 that is like thestrap lock 44 of FIG. 8, except that, rather than the plunger 46 of FIG.8, a ball 52 is fitted into of a receiver hole 51, with biasing of ball52 provided by installation of a spring 53 within that receiver hole. Aball check-type lock is thereby formed. The ball 52 is preferablyretained within the hole 51 as by bradding the area around the lip ofthe receiver hole so as to lessen the hole diameter after the ball andspring are installed therein. A permanent seat of the ball and spring inthat hole is thereby provided with the spring 53 compressed therein. Thestrap lock of this embodiment, and the embodiment described with respectto FIG. 8, function similarly, with ball 52 substituted for plunger 46,and spring 53 functioning like spring 47, both arrangements providing areleasable locking of the strap to the receiver. With both the straplock 44 of FIG. 8 and the strap lock 50 of FIG. 9, release is preferablyaccomplished by a person pushing horizontally with the heel of his handagainst the rear sight 33 of the strap so as to urge that top strapforward, the plunger or ball is forced against spring biasing to movethe plunger or ball out of the receiver hole.

FIG. 2 shows a forward or toe end 41a of the receiver top strap 31overhanging and closely fitting against a rear end 37a of the feed block37. So arranged, the feed block is restrained from vertical movement atend 37a. Shown best in FIGS. 2 and 12, the other or opposite feed blockend 37b includes a pair of spaced apart ears 54 that are preferablyarcuate in shape and project outwardly and perpendicular therefrom.Shown in FIG. 2, the arcuate ears 54 will align with to slide intocomplementary arcuate slots 57 that are formed in opposite parallelsides of a breech 56 of barrel 55. With the barrel and receiver groupssecured together as shown in FIGS. 1, 2, 10 and 11, the feed block ismaintained on one end 37b by the close coupling of arcuate ears 54fitted in the arcuate slots 57 in barrel 55, with rear end 37a held inplace by the overhanging end 41a of the receiver top strap, the feedblock thereby exactly aligned in the receiver such that the throat 60top will be in proper alignment to the cartridge exhaust and to the drummagazine fitting thereover, as shown in FIG. 1, with the throatundersurface in alignment with the barrel breech 56. Cartridges fromthat magazine exhaust thereby pass through the throat and arepositioned, in turn, for pick-up from the feed block throat undersurfaceby the forward of the firing pin end of bolt 35. The feed block, as thebolt end travels thereunder, is arranged to provide for camming eachcartridge downwardly into the barrel breech, with the bolt picking upthe cartridge and, at its limit of forward travel, firing the cartridge,and, thereafter, traveling rearwardly to pull the spent casing therefromand eject it through a receiver discharge or ejection port 58, thecasings flowing therefrom past the trigger guard 28.

In securing the feed block to the gun 20, the feed block arcuate ears54, as shown in FIG. 11, are fitted into the barrel arcuate slots 57and, prior to installing the described top strap 31 over the steppedportion of the receiver 30 top, the feed block is rotated into theposition shown by the solid line representation and the top strap 31 isthen slid thereover. Alternatively, the feed block rear end 37a can beslid under the top strap end 41 and rotated onto its seat on thereceiver, the feed block ears fitted into the barrel slots at the timethe barrel group is installed to the receiver group.

Excepting the described feed block arcuate ears 54 that interlock withthe described barrel arcuate slots 57 and provide for maintaining thefeed block positioning relative to the barrel breech, the cartridge feedblock of the present invention is substantially like the cartridge feedblock shown and described in the cited patent by Brandstatter et al.,U.S. Pat. No. 3,969,980. Feed block positioning in this Brandstatterpatent is maintained by pin holes or openings formed through the feedblock that receive alignment pins that extend vertically upward fromopposite sides of the receiver. While this earlier pin arrangement didprovide for feed block positioning, it did not restrain verticalmovement of that feed block. The present invention, therefore, improveson the earlier structure by providing the arcuate ears 54 to fit intothe barrel arcuate slots 57 to both position and lock the feed block 37in the assembled weapon.

Except as set out above relative to arcuate ears 54, the feed block 37is like the earlier feed block of the Brandstatter et al. patent.Therefore, the feed block 37 components and their function are likethose of like the earlier feed block, and so will be described onlybriefly herein. Feed block 37 is shown in FIG. 10, with the internalcomponents thereof shown in broken lines, and in a perspective view ofFIG. 12. Shown therein, the feed block 37 includes an upper or topsurface 59 that, with the feed block positioned to receiver, isjuxtapositioned with the undersurface of the magazine 36 that isretained between the barrel and receiver, the feed block including alongitudinally extending cartridge throat 60 formed therethrough that isof a length and width sufficient to permit a cartridge to feedtherethrough, which throat is aligned to the magazine exhaust. The feedblock, as described in the above-cited patent, perferably consists ofsandwiched upper and lower plates or layers, the upper or first layerincluding a transverse rim or edge 61 on each long side of the cartridgethroat adjacent the magazine exhaust that is included to provide asmooth funneling action into the throat to cartridges fed therein fromthe magazine feed. Below the beveled edges, in the lower or secondlayer, are arranged two laterally opposed coplaner leafs 62 that arepivotally connected and biased by springs 64 to bring edges 63 thereofinto engagement with the sides of a cartrige fitted therein. The springbiasing is such that, as a cartridge is picked up from the feed block bythe firing pin end of the bolt 35, a following cartridge will be forced,by the action of the magazine spring, to overcome that biasing topartially pass through the feed block throat, and is retained thereinbetween edges 63. The cartridge casing rim will then come to rest onrear flanges 65 of that lower or second layer for pick-up from theundersurface thereof by the bolt edge for delivery into the barrelbreech, firing, and ejection of the spent casing as described.

Shown in FIGS. 2 and 11, the barrel group installation arrangement ofthe present invention, for joining it by a single screw to the receivergroup, includes a receiver barrel positioning pin 66 that is securedwithin the receiver so as to extend laterally thereacross, justextending or projecting above the receiver bottom 30b, and is locatedback from the forward or barrel connecting receiver end 30a, whichpositioning pin is arranged to seat in a lateral groove 67 formed in thebarrel 55, which groove is forward from the barrel breech 56 or towardthe barrel muzzel end. The interaction of the barrel groove 67 seatedonto pin 66 provides a pivot coupling that acts also to align andposition the barrel in that receiver group. After the barrel lateralgroove 67 is so seated onto the receiver barrel positioning pin 66, thebarrel can be rotated to bring the breech 56 into the receiver to aligna tapped or threaded hole 68 formed radially into the barrel intoalignment with an upper threaded end 70 of a barrel retaining screw 69.The barrel retaining screw, described hereinbelow, is preferably formedto have a smooth center area 78 for fitting into and being maintained infree-wheeling arrangement in a hole 79 formed through the receiverbottom 30b. The preferred barrel retaining screw arrangement is shownturned out of barrel threaded hole 68 in FIG. 14, and is shown turnedinto that hole in FIGS. 13 and 15. The barrel retaining screw 69, shownin FIGS. 2, 11, 13, 14, and 15, is preferably assembled to include aknob 71 with a center longitudinal hole 74 that is fitted onto anunthreaded shank end 77 of the screw, which knob preferably includes agreater diameter knurled surface 72 for facilitating a person turningthat knob with their fingers to assemble and disassemble the gun barrelgroup from the receiver group. The barrel retaining screw includes alower threaded portion or segment 73 that is turned into threads tappedinto the knob center hole 74. Locking of the knob to the screw isprovided by installation of set screws 75, shown best in FIG. 2, thatare fitted into and turned into opposing radial threaded openings 76formed into the knob knurled surface 72 to intersect the knob centerhole 74. Shown in FIG. 13, the set screws are turned against theunthreaded shank end 77 of the barrel retaining screw 69, lockingthereto. Shown in FIGS. 2, 13, and 15, the open unthreaded center area78 of the barrel retaining screw provides for some vertical travel andallows the barrel retaining screw to free-wheel in the hole or opening79 formed through the receiver bottom 30b. The opening 79 includes aninwardly projecting lip 79a that provides a stop butt against a first orlower thread flight of threaded end 70 to block withdrawal of thatretaining screw upper threaded end. So arranged, to mount the barrelretaining screw in the receiver, the screw shank end 77 is fittedthrough to extend from the receiver opening 79 and the knob 71 is theninstalled thereto, with the knob set screws 75 turned to engage and bindagainst that shank end. To install the barrel group to the receivergroup, the barrel lateral groove 67 is seated on the receiverpositioning pin 66, and the barrel group is rotated therearound to bringthe barrel breech end 56 into the receiver. The upper threaded end 70 ofthe barrel retaining screw 69 thereby aligns so as to be turned into thebarrel threaded hole 68. Turning the barrel retaining screw causes thebarrel to be drawn snugly into the receiver, providing one point oflocking contact, with the pivot arrangement of the barrel positioningpin and receiver barrel groove providing a second metal-to-metal pointof contact. The two points of metal-to-metal contact exactly positionand rigidly lock together the barrel group relative to the receivergroup. This rigid coupling of the barrel and receiver groups also fixesthe head space distance between the firing pin end of bolt 35 and thebarrel breech end 56, which optimum distance is thereafter maintainedwithout adjustment.

The present invention provides a simplified interlocking arrangement ofthe components of the gun 20 of the present invention, facilitatingassembly and disassembly of the barrel and receiver groups, whichinterconnection also provides for setting and maintaining feed blockalignment and positioning and sets the weapon head space. Thereby, bymanual turning of a single barrel retention screw only the weaponcomponents are rigidly coupled together. A person, in a field setting,can therefore, in a matter of seconds only, disassemble the gun into itscomponents assemblies, including removing the bolt and bolt spring fromthe receiver, for cleaning and maintenance, and in a like time periodcan reassemble the weapon.

Herein has been described the perferred combination of components andthe components themselves making up the submachine gun of the presentinvention. It should be understood that the present disclosure appliesto both automatic and semiautomatic weapons, and is made by way ofexample only, and that changes can be made thereto without departingfrom the subject matter coming within the scope of the following claims,which claims we regard as our invention.

We claim:
 1. A coupling arrangement for rigidly connecting togetherreceiver and barrel groups in proper registry with a feed block of a guncomprising, a pin fitted laterally through and between opposite sides ofa rectangular shaped receiver, which pin projects upwardly from andacross a receiver bottom and is to receive a complementary lateralgroove formed in a gun barrel of the barrel group, which groove isforward from a breech end and is to function as a pivot such that whenthe barrel group is rotated therearound to pivot the barrel breech intothe receiver, a radial threaded hole formed in the barrel will alignwith an opening formed through said receiver bottom the barrel breechend, along opposite sides thereof including identical arcuate groovesformed therein that are open to receive complimentary ears that eachextend from opposite sides of a feed block when said barrel group is sopivoted into said receiver, said feed block end thereby being locked tosaid barrel group in registry with said barrel breech; and a barrelretaining screw maintained in said opening in said receiver bottom thatincludes a threaded end for turning into said barrel radial threadedhole, to draw the barrel group into position in said receiver,maintaining said feed block therein, and providing points of rigidconnection at said barrel retaining screw and said pivot.
 2. A couplingarrangement as recited in claim 1, wherein the barrel retaining screw isfree-wheeling in the receiver bottom opening and includes a large headto accomodate manual turning.
 3. A coupling arrangement as recited inclaim 1, wherein the pin is round.